Background: Measurement of carcinoembryonic antigen (CEA) has been widely applied to detect recurrence, especially of colorectal carcinoma. The validity however, is still controversial. We investigated serial changes in CEA values to calculate whether the CEA doubling time and half-life time could predict metastatic progression or prognosis in colorectal carcinoma.

Methods: Pre- and post-operative serial serum CEA contents were determined in 22 cases of colorectal cancer with or without metastasis. CEA values were determined by enzyme immunoassay (EIA). Patients were assigned depending upon survival time (within vs. more than 18 months after primary resection) for assessment of CEA doubling time. From the gradient of the semi-logarithmic CEA graph, the preoperative doubling time was calculated and the postoperative half-life time was estimated according to the diagnosis of metastases within 2 years after primary resection [metastasis (+) or (-)].

Results: In spite of the effect of curative re-operation of metastatic lesions or of postoperative adjuvant chemotherapy, the CEA doubling time of the groups showed a relation with prognosis (p = 0.045, Student's t-test) when the patients were divided into >18 and < or =18 months survival time. The CEA half-life time of the groups without overlooked metastases was statistically longer than those with (mean +/- SD 8.01 +/- 2.07 and 4.33 +/- 1.11, respectively, p < 0.01, one-factor ANOVA test). Clearance (k) showed a significant difference between the groups (p < 0.001, Student's t-test).

Conclusion: The CEA doubling time appeared to be a less independent prognostic factor, whereas prolongation of the CEA half-life time might potentially suggest the existence of overlooked synchronous metastases from colorectal carcinoma.